Elastomeric materials have long been used to make shock isolator pads for missiles. The shock isolator pads usually employ prebuckled struts to support the missile in its launch tube, provide shock mitigation, and damp vibrations. Tolylene diisocyanate terminated polyoxytetramethylene based prepolymers, such as Adiprene L-100 or L-167, extended with 4,4'-methylenebis(orthochloroaniline)-MOCA- have been used in the manufacture of these structural members, as taught by Mendelsohn et al. in I&EC Product Research & Development, Vol. 10, p. 14-25, March 1971 and Vol. 14, p. 181-189, September 1975, and by Meier et al. in Resins for Aerospace, C. A. May Editor, ACS Symposium Series 132, American Chemical Society, Chapters 14 and 15, Washington, 1980. Both the tolylene diisocyanate and the 4,4'-methylenebis(orthochloro-aniline), however, are now believed to present severe toxicologic problems.
Mendelsohn et al., in U.S. Pat. No. 4,485,719, filed on Apr. 8, 1982 provided substitutes for these materials, utilized in a high modulus, highly rigid missile launch seal, or in certain types of stiff shock isolator pads. The polyurethane used was a cured admixture of from about 5.0 to 5.4 parts by weight prepolymer per 1 part by weight chain extender, where the prepolymer was made from about 3.1 to 3.4 moles of 4,4'-diphenylmethane diisocyanate; and about 0.22 to 0.32 mole of low molecular weight triol, per 1 mole of polyoxytetramethylene glycol. In most situations, such a formulation, while very appropriate for missile launch seals, was too rigid for most shock isolator pad use. Thus, there is a need for substitute polyurethane elastomers that can be utilized in the manufacture of highly flexible shock isolator pads that will be in circumferential contact with launchable missiles.